The present invention generally pertains to fastening machines and more particularly to a pierce nut insertion tool.
It is well known to install pierce nuts in sheet metal panels. Exemplary installation machines are disclosed in the following U.S. Pat. No. 3,108,368 entitled “Method of Sizing and Installing a Pierce Nut in a Panel” which issued to Steward on Oct. 29, 1963; U.S. Pat. No. 6,257,814 entitled “Self-Attaching Fastener, Method of Forming Same and Method of Attachment” which issued to Müller on Jul. 10, 2001; U.S. Pat. No. 6,925,698 entitled “Method of Feeding and Installing Self-Attaching Nuts” which issued to Goodsmith et al. on Aug. 9, 2005; and U.S. Pat. No. 6,957,483 entitled “Self-Diagnosing Pierce Nut Installation Apparatus” which issued to Woods on Oct. 25, 2005. All of these patents are incorporated by reference herein. Various of these conventional machines, however, require complex cam-rotated fingers or spring loaded ball bearings biased to engage a separated nut aligned with a ram prior to ram extension; these complex moving parts are subject to wear and damage, are difficult to service, and are of heightened concern since they also contact against the high force ram. Furthermore, these conventional machines do not allow for independent control and timing of a nut feeding mechanism. Moreover, it can be a challenge to strip the nut from connective wires, and then orient and center the pierce nut relative to the die throughout the ram and nut travel.
U.S. Pat. No. 5,172,467 entitled “Installation Apparatus for Installing Self-Attaching Fasteners” which issued to Muller on Dec. 22, 1992, discloses a pneumatically driven piston for shuttling a single stud. This patent is incorporated by reference herein. This apparatus, however, is overly simplistic and can only push a single stud from an intermediate supply tube per stroke, thereby incurring long cycle times and misfeed concerns. The piston is externally mounted and requires expensive external valve control and connections by the user.
In accordance with the present invention, a pierce nut installation tool is provided. In another aspect, a pierce nut feeding mechanism has a mechanically independent driver or actuator from that of a punch. Yet another aspect provides a fluid actuated pierce nut feeder, more preferably with an internal valve and/or control arrangement to advantageously reduce installation complexity and increase cycle speed. A further aspect of the present tool employs a member, attached to a punch, that retains a pierce nut prior to fastening of the nut to a workpiece. A serviceable pierce nut feeding mechanism is provided in yet another aspect of the present tool.
The present tool is advantageous over conventional machines. For example, the independent actuator for the present pierce nut feeding mechanism allows the operator to change settings on a programmable controller in order to vary a stroke length or end distances, and also to vary the timing of the feed mechanism relative to a punch actuator. This can additionally be varied between different types of pierce nuts and workpiece configurations. In the internally valved and/or controlled configuration, external customer installation complexity is reduced while still allowing for the force and cycle speed benefits of fluid actuation; expensive sensors for the piston location are also not required with this approach. The present tool advantageously accurately centers and orients the pierce nut relative to the punch and die with minimal tool components. A manual feeding mechanism for the pierce nut is also employed in addition to an automatically powered actuator. Furthermore, the low profile body and nut feeding mechanism of the present tool is advantageously configured to place the pierce nut closer to edges and flanges of workpieces than many traditional machines. The present tool provides more space between a bottom of a punch-side tool and the workpiece. Additional advantages and features of the present invention will be found in the following description and accompanying claims, as well as in the appended drawings.